The impressive developments in micro / nano-electro-mechanical-systems (MEMS; NEMS) have led to a new class of
chemical and biological sensors based on micro and nano cantilevers. This work focuses on fabrication challenges of flat
cantilevers exhibiting well-controlled, uniform and reproducible mechanical performance. Our experimental study is
based on cantilevers made of crystalline silicon (c-Si), using SOI wafers as the starting material and using bulk
micromachining. Experimental results on fabrication and characterization of composite porous silicon-crystalline silicon
microcantilevers made of SOI wafers are also presented, where the porous silicon surface provides an excellent interface
for immobilization of the biosensing layer. The optimal geometric design of microcantilevers depending on the
application as well on the selected sensing mode (static or dynamic) is considered. The innovative aspects and open
issues of NEMS/MEMS cantilever-based biosensors are addressed.
A novel magnetic actuated polymer optical platform is integrated into a Michelson interferometer type Fourier transform
infrared spectrometer. The proposed advantages of the novel platform over existing approaches, such as MEMS
spectrometers, or bulky FTIR systems, include millimeter range dimensions providing a large clear aperture and enabling
conventional machining for device fabrication, a controllable AC and/or DC motion both in rotational and translational
modes, and low frequency operation. It has been demonstrated that the platform is capable of achieving 400μm DC
deflection in ambient pressure in the translational mode, and a total optical scan angle exceeding 60 degrees in the
resonant rotational mode. A Michelson type Fourier transform spectrometer was built using a retro-reflector bearing FR4
platform and a spectral resolution of 25cm-1 is demonstrated with this setup. In addition, possible use of the same
platform in various other spectrometer configurations and methods to improve the motion precision are discussed.
A grey body emitter based on a microcavity array with Pt-heater on the backside is presented. The microcavity array is
made by electro-chemical etching of silicon. It has been shown in a previous work, that this emitter has especially in the
spectral region >8 μm significantly higher emissivity than commercial available emitters.
Due to the thin-film technology of MEMS-based emitters, these types can be typically operated with a maximum
temperature of 700°C to 800°C. Higher temperature causes degradation of the heater. But higher temperatures also mean
an enhancement in radiation power and thus open a wider area of application.
The presented work shows a temperature enhanced thermal emitter with a ceramic heater passivation. Short time tests
show the possibility of a maximum temperature of 1000°C.
The part of light emitted by the microcavities in comparison to the whole device as well as the influence of the pore size
concerning the emitted spectral range is investigated. The results are the basis for a redesign of the microcavity array for
an enhancement of the geometry tuned emissivity.
MOEMS-based thin silicon membrane mirrors with a useable diameter of 5mm and fast (up to 1kHz) tunable focal length
(80 mm to 1m) have been realized. A ring shaped counter electrode is used to achieve a parabolic membrane deformation
by electrostatic forces. A circular kerf at the outer perimeter of the membrane provides a soft suspension to the rim and
thus reduces the needed driving voltage. FEM has been used for optimisation of the design, especially of the soft
suspension, which is realized by a controlled thinning of the outer rim of the Si-membrane.
A critical issue for demanding applications is the membrane distortion induced by material stress and the fabrication
process. Membrane residual stress reduction has been obtained by using SOI-technology (c-silicon) and by optimisation
of the Al deposition process (Al-coated Si-membrane).
For dynamic tests of the optical mirror properties a stroboscopic interferometer has been realized. A pulsed laser diode
with a pulse duration of 10μs is used as a light source which is synchronized with the modulated electrical field driving
the membrane mirror. The interference pattern is recorded with a CCD and evaluated with conventional phaseshift
techniques. The geometry is similar to a Mach-Zehnder interferometer. The reference path length can be varied with a
piezoceramic to induce the phase shift.
Microsystems technology may be employed for the conceptualization and fabrication of new types of tunable micro-optical
components. Tunable polymer membrane-based micro-lenses, tunable liquid lenses and lens arrays as well as deformable
membrane mirrors are presented here.
This paper reports fabrication methods of polymer-based micro/nano optical structures based on replica molding.
Various molds have been used: polymer, silicon, and SiO2-based. Different types of treatment and release agent were
investigated in order to achieve an optimum demolding. Diffractive optical elements, micro-lenses and antireflective
layers have been obtained in commercial or doped polymers with controlled refractive index. The quality of the
replication was investigated using optical microscopy, SEM, profilometry and functional tests. The micro-optical
components can be transferred onto silicon silicon chip with photodetectors, or photonic integrated circuits using
This paper presents a novel SU-8 polymer-based grating light modulator fabricated using conventional process
technology which requires no expensive equipments and materials. A set of fifty 2.5μm-thick SU-8 micro beams of
20μmwidth x 100μm-length is patterned by photolithography on the aluminum sacrificial layer to form a grating. The
micro beams are arranged in parallel with an inter-beam gap of 20μm. The wide inter-beam gap tolerates low patterning
precision. Narrow air gaps of 0.5μm beneath the micro beams are formed by combination of wet-etching of the
aluminum sacrificial layer and freeze drying method, where cyclohexane is chose as sublimation liquid because of the
high freezing point and the ease of sublimation. When a voltage is applied across the upper and lower electrodes to
attract the micro beams to the substrate, neighboring micro beams are actuated to deflect in phase and the optical path
length between the upper electrode/mirror on the micro beam and the lower mirror on the substrate decreases by quarter
wavelength, the 0th and 1st order diffracted light intensities vary from maximum and minimum, respectively, or vice
versa. The voltage to obtain maximum modulation for HeNe laser beam of 632.8nm wavelength is 70V. The rise and fall
response times of the light modulation are 3.08 microsecond and 4.63 microsecond, respectively.
Optofluidics is the process of integrating the capabilities of optical and fluidic systems to achieve novel
functionalities that can benefit from both. Among the novel capabilities that an optical system can bring to the table is
the ability to manipulate objects of interest in a liquid media. In the case of biological samples, the objects of interest
consist mainly of cells and viruses, whereas in applications such as nanoelectronics, manipulation of nanoparticles is of
interest. In recent years, optoelectronic tweezers (OET) has emerged as a powerful technique for manipulation of
microscopic particles such as polystyrene beads, cells, and other biological samples and nanoscopic objects such as
In this paper, we will focus mostly on recent advances in the optoelectronic tweezers technology, including
characterization of optoelectronic tweezers operational regimes, manipulation of biological samples such as cells in highconductivity
physiological solutions with translation speeds higher than 30 μm/s, manipulation of air bubbles in
silicone oil media with speeds up to 1.5 mm/s, and exploring the limits on the smallest particle that OET is capable of
trapping. These advances all contribute immensely to the functionalities of OET as an optofluidic system.
InP based tunable optical MEMS devices, such as Fabry-Perot filters, VCSELs, photodiodes, consist of two distributed
Bragg reflectors (DBRs) and a cavity. Tuning of the filter wavelength is achieved by electrostatic actuation of the two
DBRs which are p-doped and n-doped, respectively, and reversely biased. The cavity and the DBRs consist of a stress
compensated InP/airgap structure which is fabricated by sacrificial layer removal, using FeCl3 wet etching of InGaAs
layers. In this work we investigated the influence of p-and n-type conductivity on the etching process. We observed that
the sacrificial layer etch rate of n-InGaAs is 7 times slower than the p-InGaAs. This influences the stress in the n-DBR
section of the tunable device. Based on these results novel wavelength tunable optical devices with multiple InP
membrane/airgap structures will be designed.
Polytetrafluoroethylene (PTFE) is an ideal material for use in microfluidic applications, such as
industrial inkjet and biomedical analysis devices. PTFE has outstanding physical properties; such as chemical inertness and resistance to chemical corrosion, even when exposed to a strong acid, alkali and oxidants. Its properties provide for superior electrical insulation and thermal stability, which is not affected by wide ranges in temperature and frequency. Its non-absorption of moisture makes it a perfect material for consideration in micro-fluidic devices used in chemical analysis, fluidic photonic sensors and biomedical diagnostics. This paper presents an overview of a unique fabrication method that incorporates a variety of elements to establish a processing technique that can form micro channels, complex filter arrays and reflective micro mirror structures into PTFE materials for such applications. Using a modified isostatic compression molding process, this new technique incorporates the addition of a vacuum to assist in the reliable molding of micron structures and further densification of the fused or semi-fused PTFE. Various micro-structured electroformed and micro-machined shims are demonstrated to form small microstructures into the surface of the PTFE material. The combination of the vacuum and the electroformed shim within the molding process noticeably increases the precision, reproducibility and resolution of microstructures that can be realized. The paper will describe the molding hardware involved, process parameters and the resulting microfluidic channels and complex filter and capillary structures formed. Function testing and metrology of the micro-structure geometry formed on each sample will be compared to the original design mandrel geometry.
Proc. SPIE 6993, Technology development for micromirror arrays with high optical fill factor and stable analogue deflection integrated on CMOS substrates, 69930D (25 April 2008); doi: 10.1117/12.787015
At Fraunhofer IPMS Dresden micromechanical mirror arrays are developed and fabricated using a high-voltage CMOS
process for applications such as lithographic mask writers and adaptive optics. Different approaches for the fabrication of
micromechanical mirror arrays with up to 1 million analogue addressable pixels in a MEMS-on-CMOS technology are
discussed: sacrificial layer technologies of 1-level actuators made from a single Al-TiAl-Al structural multilayer or 2-level actuators with an additional TiAl hinge layer respectively. Also the fabrication of single crystalline Si micro-mirrors
using layer-transfer bonding is discussed.
Processing of GaN-AlInN-GaN epitaxial trilayers into 3-dimensional microstructures, using a combination of vertical
dry etching and lateral wet etching, is discussed. The AlInN layers were grown so as to have an InN mole fraction close
to the value of 17% required for lattice matching with GaN. Inductively coupled plasma etching with chlorine-argon gas
mixtures was used to define mesa features with near-vertical sidewalls. Refluxing aqueous solutions of nitric acid of 2
molar concentration allowed highly selective lateral etching of the AlInN interlayers exposed on the mesa sidewalls,
providing a novel sacrificial layer technology for the III-nitride materials. Lateral etch rates of 0.14-0.21 μm/hr were
observed for 100-nm AlInN interlayers. Two distinct applications are discussed. In one example, lateral etching of an
AlInN layer was used to expose the underside of epitaxial GaN disks for fabrication of planar microcavities. Here,
retention of an optically smooth GaN (0001) surface on the underside of the disks is critical. Microbridges with potential
for development as sensors were also demonstrated, and the deformation of these structures provides a sensitive probe
of the local strain state of the undercut GaN layer.
Microfluidic devices play a crucial role in biology, life sciences and many other fields. Three aspects have to be
considered in production of microfluidic devices: (i) material properties before and after processing, (ii) tooling and
processing methodologies, and (iii) measurements for process control. This paper presents a review of these three areas.
The key properties of materials are reviewed from both the production and device performance point of views in this
paper. The tooling and processing methodologies considered include both the direct tooling methods and the mold based
processing methods. The response of material on the production parameters during hot embossing process are simulated
for process control and product quality prediction purpose. Finally, the measurements for process control aspect discuss
different measurement approaches, especially the defect inspection, critical dimensional measurements, bonding quality
characterization and checking functionality. Simulation and experimental results are used throughout the paper to
illustrate the effectiveness of such approaches.
Micro-opto-electromechanical systems (MOEMS) based on micromechanical mirrors can be used as key elements for
light guiding, steering and concentration. We propose micromechanical mirror arrays for light concentration on
photovoltaic modules. The semiconductor materials for solar cells are the most expensive components of a photovoltaic
system. One of the ways to reduce cost is to use light concentration by focusing sunlight onto small solar cell areas using
optical components such as lens systems. The whole system requires an external rotation mechanism to track the suns
position. As an alternative, we propose and implemented micromachined mirror arrays to concentrate light. This allows
precise dynamic light steering onto the solar cell module. These micromirror arrays can be electrostatically tuned to track
the sun position or the maximum of the brightness distribution in the sky. The micromirror arrays are located in a sealed
environment and, therefore, insensitive to external influences, such as atmosphere and wind. The advantages of the
micromachined mirrors based concentrator photovoltaic systems are dynamic light steering onto solar cells, mass
production compatibility, long lifetime and low cost. The concept of the micromachined mirror arrays will be presented.
The experimental method of micro-/nanotensile testing for extracting the mechanical properties of small volumes of
materials ( e.g. free-standing thin films) has gained more and more interest, since it provides an effective way to evaluate
the actual material properties without any pre-assumptions, and consequently its results can be used as a reference for
verifying other material testing methods such as nanoindentation testing, laser acoustic method, etc. As one of the key
components within a nano-tensile testing system, here a MEMS-based nano-force actuator is presented, which is
developed on the basis of an electrostatic lateral comb-drive, having an output force resolution up to 3 nN with a
maximum output force up to the mN range. A fixed gripper is integrated into the nano-force actuator, with which a free-standing
thin film specimen with matched holder can be easily coupled and tested. Design and numerical simulation of
the nano-force actuator with the help of finite element analysis (FEA) are detailed. A calibration system is developed,
which employs a single-frequency laser interferometer as an SI-traceable standard for the determination of the actual
displacement-to-square-voltage ratio (d/V2) of a prototype of the actuator. Calibration results reveal that the actual
performance of the prototype coincides quite well with the designed specifications. With atomic force microscope
(AFM) the error sources within the prototype are further investigated.
This paper describes a MEMS (micro-electromechanical systems) modulator suitable for optical system network
signaling. Several actuator mechanisms exist that potentially satisfied this purpose, electrostatic actuation was identified
as the most suitable for the application due to speed of operation and low power consumption. MEMS geometry and
analytical mode models were developed and applications performance estimated including multiphysics phenomena.
Finite element analysis was undertaken using the commercially available software suite, COMSOL(R), performing static
and dynamic simulations and analyses in the time and frequency domains. The proposal is that the MEMS modulator
would be integrated with other optical components encased in a hermetically sealed vacuum environment, resulting in a
lightly damped response with decaying oscillation. A two-step drive signal was developed and simulated using the multidomain,
simulation package SIMULINK®. The optimized MEMS design and two-step driver realized a MEMS optical
modulator meeting the required specification. Finally a proposal for integration within an optical transmitter assembly is
Nowadays microelectromechanical systems (MEMS) have found more and more applications in various fields of
industry and scientific researches. In the meantime, quality control to MEMS devices and equipment gains more and
more importance, in which one of the important tasks is to characterize the in-plane behaviours of MEMS, including the
in-plane displacement/deflection/deformation, vibration amplitude, resonant frequency, etc. However, due to the special
characteristics of MEMS device, this task cannot be fulfilled easily with high resolution and wide bandwidth. In order to
calibrate and to further improve the performance of MEMS actuators and sensors, in this paper, inspection of in-plane
displacement of MEMS on the basis of an atomic force microscope is discussed, in which the lateral interaction between
an AFM cantilever and a electrostatic actuator is investigated, and its potential application to determine the dynamic
behaviour of a MEMS actuators/sensors is demonstrated.